Objectives of proposed research: 1. To continue study of the structural alterations of AVP which regulate (a) antidiuretic specificity and (b) duration of action. 2. To complete the synthesis and pharmacological characterization of the known neurohypopysial peptides. 3. To design and synthesize peptides for the following possible therapeutic uses: (1) Inhibitors of oxytocin for possible use (a) in the prevention of premature deliveries and (b) for the control of ovulation. (2) Inhibitors of arginine vasopressin (ADH) for the treatment of hyponatremia resulting from the inappropriate secretion of ADH. (3) Natriuretic/diuretic peptides of potential clinical value. (4) Vasopressin analogs with selective regional vasopressor effects. To continue to provide other investigators with samples of synthetic peptides for their independent investigations.